Flow-distortion effects on scalar flux measurements in the surface layer: Implications for sensor design

1988 ◽  
Vol 42 (1-2) ◽  
pp. 19-26 ◽  
Author(s):  
J. C. Wyngaard
Keyword(s):  
Surface Layer ◽  
Sensor Design ◽  
Scalar Flux ◽  
Flow Distortion ◽  
Flux Measurements

scholarly journals Influence of the Atmospheric Surface Layer on a Turbulent Flow Downstream of a Ship Superstructure

2013 ◽  
Vol 30 (8) ◽  
pp. 1803-1819 ◽  
Author(s):  
Luksa Luznik ◽  
Cody J. Brownell ◽  
Murray R. Snyder ◽  
Hyung Suk Kang
Keyword(s):  
Surface Layer ◽  
Atmospheric Surface Layer ◽  
The United States ◽  
Naval Academy ◽  
Mean Flow ◽  
Flow Distortion ◽  
Turbulent Statistics ◽  
Sonic Anemometers ◽  
Flight Deck ◽  
Inflow Conditions

Abstract This paper describes a set of turbulence measurements at sea in the area of high flow distortion in the near-wake and recirculation zone behind a ship's superstructure that is similar in geometry to a helicopter hangar/flight deck arrangement found on many modern U.S. Navy ships. The instrumented ship is a 32-m-long training vessel operated by the United States Naval Academy that has been modified by adding a representative flight deck and hangar structure. The flight deck is instrumented with up to seven sonic anemometers/thermometers that are used to obtain simultaneous velocity measurements at various spatial locations on the flight deck, and one sonic anemometer at bow mast is used to characterize inflow atmospheric boundary conditions. Data characterizing wind over the deck at an incoming angle of 0° (head winds) and wind speeds from 2 to 10 m s−1 obtained in the Chesapeake Bay are presented and discussed. Turbulent statistics of inflow conditions are analyzed using the Kaimal universal turbulence spectral model for the atmospheric surface layer and show that for the present dataset this approach eliminates the need to account for platform motion in computing variances and covariances. Conditional sampling of mean flow and turbulence statistics at the flight deck indicate no statistically significant variations between unstable, stable, and neutral atmospheric inflow conditions, and the results agree with the published data for flows over the backward-facing step geometries.

Evaluation of methods for estimating atmospheric stability at two coastal sites

2018 ◽  
Vol 42 (6) ◽  
pp. 561-575 ◽  
Author(s):  
Lars Morten Bardal ◽  
Anja Eide Onstad ◽  
Lars Roar Sætran ◽  
John Amund Lund
Keyword(s):  
Surface Layer ◽  
Richardson Number ◽  
Atmospheric Stability ◽  
Stability Conditions ◽  
Bulk Richardson Number ◽  
Wind Speed Profile ◽  
Flux Measurements ◽  
Vertical Wind Speed ◽  
Stability Measurements ◽  
Evaluation Of Methods

Understanding the atmospheric stability conditions is important in order to obtain accurate estimates of the vertical wind speed profile. This work compares and evaluates common methods for estimation of atmospheric stability using standard meteorological mast observations. Atmospheric stability distributions from three different met-masts located at two coastal sites are calculated and compared. The atmospheric stability parameter, L is estimated using the bulk Richardson number, the surface-layer Richardson number, and calculated directly from eddy covariance flux measurements. The resulting distributions vary depending on which method is used. The atmospheric stability measurements from two masts located 3 km apart in similar terrain are compared directly. The highest correlation is found for the surface-layer Richardson number method. This method it also less sensitive to variation of measurement heights than the bulk Richardson number method.

scholarly journals Motion-correlated flow distortion and wave-induced biases in air–sea flux measurements from ships

2015 ◽  
Vol 15 (11) ◽  
pp. 15543-15570 ◽  
Author(s):  
J. Prytherch ◽  
M. J. Yelland ◽  
I. M. Brooks ◽  
D. J. Tupman ◽  
R. W. Pascal ◽  
...  
Keyword(s):  
Momentum Flux ◽  
Time Varying ◽  
Wave Interactions ◽  
Flow Distortion ◽  
Platform Motion ◽  
Flux Measurements ◽  
Wind Measurements ◽  
Dependent Flow ◽  
Measured Momentum ◽  
Wave Induced

Abstract. Direct measurements of the turbulent air–sea fluxes of momentum, heat, moisture and gases. are often made using sensors mounted on ships. Ship-based turbulent wind measurements are corrected for platform motion using well established techniques, but biases at scales associated with wave and platform motion are often still apparent in the flux measurements. It has been uncertain whether this signal is due to time-varying distortion of the air flow over the platform, or to wind–wave interactions impacting the turbulence. Methods for removing such motion-scale biases from scalar measurements have previously been published but their application to momentum flux measurements remains controversial. Here we show that the measured motion-scale bias has a dependence on the horizontal ship velocity, and that a correction for it reduces the dependence of the measured momentum flux on the orientation of the ship to the wind. We conclude that the bias is due to experimental error, and that time-varying motion-dependent flow distortion is the likely source.

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